An enormous hawthorn tree has been discovered on a farm in the Stockton district.

With a girth measuring just over 1.3 metres it is in the top 30 of the biggest hawthorns in the UK.

Another mighty willow tree was also found. Measuring 5.6 metres in girth,it is thought to be the 5th largest of this species recorded so far in the country.

The trees were discovered by surveyors working with the Wildflower Ark on their hedgerow survey of Stockton.It was generally believed that the district, along with most of the Tees Valley, did not support many really big or ancient trees.

Until recently local timber was a very important resource for building, local manufacture and for pit props in Cleveland's extensive ironstone mines.

As soon as trees were big enough to provide timber they were chopped down and it is perhaps only in the last fifty years that our trees have been allowed to grow old gracefully.

Previous to the discovery of these specimens in Stockton, it had been thought that the area's biggest trees might be small-leaved lime trees, growing in the Kilton Beck Valley in East Cleveland.

These trees, estimated as being between 600 and 1000 years old are a series of young stems growing from huge single stools, which range in width from about 2.5 metres to a giant 10 metres. Lime trees can re-grow from the base of a cut trunk and so the regular harvesting of the timber (coppicing) had accounted for the long term survival of these trees and for the multiple stems present.

It is difficult to define precisely what constitutes an ancient tree, but according to some experts, the number of such trees is exceptional in the UK, compared with elsewhere in Northern Europe.

An ancient tree could be described as one that is old, fat or hollow by comparison with other trees of the same type.

Some ancient trees are instantly recognisable but others can be less obvious.

A tree in natural conditions may pass through three main stages in its life: growing from seedling to a mature tree, fully mature to late maturity and finally ancient. Girth size (measurement around the trunk at 1.5 metres above the ground) is not always a good indicator of age.

Different species vary enormously in girth - an ancient oak of more than 6m and would be roughly the same age as a birch of about one metre.

The cause of the ancient tree is being championed by the Woodland Trust. They believe that there are a lot of ancient trees scattered across our countryside yet to be found.

They are concerned that these fantastic heritage features cannot be properly protected until we know where they all are.

The Trust has set up a website that allows the UK's ancient trees to be mapped and it is through this service that the Wildflower Ark were able to record and compare the discoveries that they had made in Stockton.

For loads more information about ancient trees,visit www.woodland-trust.org.uk, a site which contains the Tree Register of the British Isles and includes pictures of ancient trees of different species.

To work out the age of a large tree look for the Forestry Commission Information Note on estimating the age of large and veteran trees in Britain at www.forestry.gov.uk.

If you are interested in the Ancient Hedgerows project, please contact Wildflower Ark on 01642 576611 and ask for Martin or Jessica, or email wildflowerark@hotmail.com.

They would also like to hear of any big or ancient trees that you know about.